A 72-year-old man presents to your clinic with a 4-month history of worsening shortness of breath. His exercise tolerance decreased, he has been having chest pains and lightheadedness. He also changed his shoes because of swelling in both feet. He finds that he becomes short of breath after working a couple of hours in an 8 hour work day. He awakens at night, gasping for breath. He has to prepare himself with pillows in order to sleep. His temperature is 99 ⁰ F, heart rate is 62 beats per minute, respiratory rate is 17 breaths per minute, and blood pressure is 190/75 mm Hg. On physical examination, his apical impulse is displaced to the left and downard. There are rales over both lower lung fields. On cardiac auscultation, there are three distinct murmurs: a high-pitched, early diastolic murmur loudest at the left lower sternal border, a diastolic rumble heard at the apex, and a crescendo–decrescendo systolic murmur heard at the left upper sternal border. Chest x-ray film shows cardiomegaly and pulmonary edema. Of the following, which is the most likely diagnosis in this patient?
